Electronic Devices With Flexible Display Cover Layers

ABSTRACT

An electronic device may have a hinge that allows the device to be flexed about a bend axis. A display may span the bend axis. To facilitate bending about the bend axis without damage, the display may include a display cover layer with a flexible portion. The flexible portion of the display cover layer may be interposed between first and second rigid portions of the display cover layer. The display cover layer may also include a layer with self-healing properties. The layer of self-healing material may be formed across the entire display cover layer or may be formed only in the flexible region of the display cover layer. The display cover layer may include a layer of elastomer in the flexible region of the display cover layer for increased flexibility. Self-healing may be initiated or expedited by externally applied heat, light, electric current, or other type of external stimulus.

This application is a division of non-provisional patent applicationSer. No. 17/879,705, filed Aug. 2, 2022, which is a division ofnon-provisional patent application Ser. No. 16/774,948, filed Jan. 28,2020, now U.S. Pat. No. 11,444,268, issued Sep. 13, 2022, which claimsthe benefit of provisional patent application No. 62/824,168, filed Mar.26, 2019, which are hereby incorporated by reference herein in theirentireties.

FIELD

This relates generally to electronic devices, and, more particularly, toelectronic devices with displays.

BACKGROUND

Electronic devices often include displays for presenting images to auser. Displays are typically formed from rigid planar substrates.Although satisfactory in many situations, rigid displays such as thesemay be difficult to integrate into certain devices, such as devices withbendable housings.

SUMMARY

An electronic device may have a hinge that allows the device to beflexed about a bend axis. A display may span the bend axis. Tofacilitate bending about the bend axis without damage, the display mayinclude a display cover layer with a flexible portion. The flexibleportion of the display cover layer may be interposed between first andsecond rigid portions of the display cover layer in one example.

During operation of an electronic device, the display cover layer forthe electronic device may be scratched or dented. To improve theaesthetics of the electronic device, it may be desirable for thepresence of scratches and dents to be minimized. To help mitigate thenumber of dents, scratches, or other imperfections in a display coverlayer, the display cover layer may include a layer of self-healingmaterial.

The layer of self-healing material may be formed across the entiredisplay cover layer or may be formed only in the flexible region of thedisplay cover layer. The display cover layer may include a layer ofelastomer in the flexible region of the display cover layer forincreased flexibility. The layer of self-healing material may cover thelayer of elastomer in the flexible region.

Self-healing may occur in the layer of self-healing material withoutprompting (e.g., when the self-healing coating is dented, the materialof the coating may fill the dent even without external intervention).Alternatively, the self-healing may be initiated or expedited byexternally applied heat, light, electric current, or other type ofexternal stimulus.

When heat is used as a stimulus for the self-healing process, thedisplay cover layer may include transparent conductors that form aheating layer in the display cover layer. The heating layer may be usedto generate heat to stimulate self-healing. The heating layer may beused to generate heat in response to user input, according to apredetermined schedule, or when the electronic device is charging.

To promote flexibility in the display cover layer, the display coverlayer may include a transparent dielectric layer with slits. The slitsmay be filled with an index-matching material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device havinga display in accordance with an embodiment.

FIG. 2 is a schematic diagram of an illustrative electronic devicehaving a display in accordance with an embodiment.

FIGS. 3 and 4 are cross-sectional side views of electronic devices withflexible displays in accordance with an embodiment.

FIG. 5 is a diagram of an illustrative display with an array oflight-emitting pixels in accordance with an embodiment.

FIG. 6 is a cross-sectional side view of a display showing how a displaycover layer may have a flexible portion interposed between rigidportions in accordance with an embodiment.

FIG. 7 is a cross-sectional side view of a display that includes adisplay cover layer with a layer of self-healing material in accordancewith an embodiment.

FIG. 8 is a cross-sectional side view of an illustrative display havinga display cover layer formed from multiple layers of transparentdielectric material in accordance with an embodiment.

FIG. 9 is a cross-sectional side view of an illustrative display havinga display cover layer with a layer of elastomer formed in a flexibleregion of the display cover layer in accordance with an embodiment.

FIG. 10 is a cross-sectional side view of an illustrative display inwhich the display cover layer includes a self-healing coating across thedisplay cover layer and an elastomer layer in the flexible region of thedisplay cover layer in accordance with an embodiment.

FIG. 11 is a cross-sectional side view of an illustrative display inwhich the display cover layer includes a self-healing coating across thedisplay cover layer and a heating layer that heats the self-healingcoating in accordance with an embodiment.

FIG. 12 is a cross-sectional side view of an illustrative display inwhich the display cover layer includes index-of-refraction-matchinglayers between layers of the display cover layer in accordance with anembodiment.

FIG. 13 is a cross-sectional side view of an illustrative display inwhich the display cover layer includes a self-healing coating across thedisplay cover layer and a heating layer positioned adjacent to theself-healing coating in accordance with an embodiment.

FIG. 14 is a cross-sectional side view of an illustrative display havinga display cover layer with slits in a transparent dielectric layer in aflexible region of the display cover layer in accordance with anembodiment.

FIG. 15 is a cross-sectional side view of an illustrative display havinga display cover layer with slits in a transparent dielectric layer in aflexible region of the display cover layer and a layer of adhesivebetween adjacent transparent dielectric layers in accordance with anembodiment.

FIG. 16 is a cross-sectional side view of an illustrative display havinga display cover layer with partial slits in a transparent dielectriclayer in a flexible region of the display cover layer in accordance withan embodiment.

FIG. 17 is a cross-sectional side view of an illustrative display havinga display cover layer with three transparent dielectric layers thatinclude slits in a flexible region of the display cover layer inaccordance with an embodiment.

FIG. 18 is a top view of an illustrative transparent dielectric layerincluding slits of the type shown in FIGS. 14-17 in accordance with anembodiment.

DETAILED DESCRIPTION

An illustrative electronic device of the type that may be provided witha flexible display is shown in FIG. 1 . Electronic device 10 may be acomputing device such as a laptop computer, a computer monitorcontaining an embedded computer, a tablet computer, a cellulartelephone, a media player, or other handheld or portable electronicdevice, a smaller device such as a wrist-watch device, a pendant device,a wearable or miniature device of other types, a computer display thatdoes not contain an embedded computer, a computer display that includesan embedded computer, a gaming device, a navigation device, an embeddedsystem such as a system in which electronic equipment with a display ismounted in a kiosk or automobile, equipment that implements thefunctionality of two or more of these devices, or other electronicequipment. In the illustrative configuration of FIG. 1 , device 10 is aportable device such as a cellular telephone, media player, tabletcomputer, watch or other wrist device, or other portable computingdevice. Other configurations may be used for device 10 if desired. Theexample of FIG. 1 is merely illustrative.

In the example of FIG. 1 , device 10 includes a display such as display14 mounted in housing 12. Housing 12, which may sometimes be referred toas an enclosure or case, may be formed of plastic, glass, ceramics,fiber composites, metal (e.g., stainless steel, aluminum, etc.), othersuitable materials, or a combination of any two or more of thesematerials. Housing 12 may be formed using a unibody configuration inwhich some or all of housing 12 is machined or molded as a singlestructure or may be formed using multiple structures (e.g., an internalframe structure, one or more structures that form exterior housingsurfaces, etc.). Housing 12 may have hinge structures such as hinge 20to allow device 10 to bend about bend axis 22. Housing 12 may have firstand second housing portions that rotate with respect to each other asdevice 10 is bent (folded) about bend axis 22 using hinge 20 or otherflexible structures joining the first and second housing portions.

Display 14 may be a touch screen display that incorporates a layer ofconductive capacitive touch sensor electrodes or other touch sensorcomponents (e.g., resistive touch sensor components, acoustic touchsensor components, force-based touch sensor components, light-basedtouch sensor components, etc.) or may be a display that is nottouch-sensitive. Capacitive touch screen electrodes may be formed froman array of indium tin oxide pads or other transparent conductivestructures. A touch sensor may be formed using electrodes or otherstructures on a display layer that contains a pixel array or on aseparate touch panel layer that is attached to the pixel array (e.g.,using adhesive).

Display 14 may include pixels formed from liquid crystal display (LCD)components, electrophoretic pixels, microelectromechanical (MEMs)shutter pixels, electrowetting pixels, micro-light-emitting diodes(small crystalline semiconductor die), organic light-emitting diodes(e.g., pixels in a thin-film organic light-emitting diode display), orpixels based on other display technologies. Configurations in whichdisplay 14 has an array of light-emitting pixels such as an array oforganic light-emitting diode pixels may sometimes be described herein asan example.

Display 14 may have a portion that overlaps bend axis 22. To facilitatebending of device 10 about axis 22, all of display 14 may be formedusing flexible structures or at least the portion of display 14 thatoverlaps bend axis 22 may be formed using flexible structures. A displaycover layer or other layer may form the outermost surface of thedisplay. Display layers such these (e.g., display cover layers) may beformed from glass, plastic, and/or other transparent display cover layerstructures and may be flexible (at least where these layers overlap bendaxis 22 of device 10).

As shown in FIG. 1 , for example, display 14 may have three portionssuch as portions 14A, 14B, and 14C. In portions 14A and 14C, display 14may be flexible or may be rigid (e.g., the pixel array in these areasmay be rigid and/or the display cover layer structures in these regionsmay be rigid). Flexible portion 14B overlaps bend axis 22 and forms astrip that lies between portions 14A and 14C and that extends across thewidth of the display between opposing edges of the display. To ensurethat flexible portion 14B is sufficiently flexible to allow device 10 tobend about axis 22, display layers such as a display cover layer fordisplay 14 may be formed from a thin flexible glass or polymer layerthat accommodates bending of display 14 about axis 22 and underlyingdisplay layers (e.g., a polymer substrate, metal traces, a polarizerlayer, a touch sensor layer, adhesive layers, and other conducting anddielectric layers in an organic light-emitting diode pixel array) mayalso be formed from flexible materials and structures.

A schematic diagram of an illustrative electronic device such as device10 of FIG. 1 is shown in FIG. 2 . As shown in FIG. 2 , electronic device10 may have control circuitry 50. Control circuitry 50 may includestorage and processing circuitry for supporting the operation of device10. The storage and processing circuitry may include storage such ashard disk drive storage, nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory configured to form a solidstate drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Processing circuitry in control circuitry 50may be used to control the operation of device 10 (e.g., to processsensor signals and other input and to control adjustable components suchas a display, a heating element, etc.). The processing circuitry may bebased on one or more microprocessors, microcontrollers, digital signalprocessors, baseband processors, power management units, audio chips,application specific integrated circuits, etc.

Input-output circuitry in device 10 such as input-output devices 52 maybe used to allow data to be supplied to device 10 and to allow data tobe provided from device 10 to external devices. As shown in FIG. 2 ,input-output devices 52 may include display 14. Display 14 may be atouch screen that incorporates a two-dimensional touch sensor or may beinsensitive to touch. A two-dimensional touch sensor for display 14 maybe formed from an array of capacitive touch electrodes touch sensor orother touch sensor components (e.g., force sensors, resistive touchsensors, acoustic touch sensors, optical sensors, etc.).

Input-output devices 52 may include sensors 56. Sensors 56 may include acapacitive proximity sensor, a light-based proximity sensor, a magneticsensor, a force sensor such as a force sensor that gathers user input, atouch sensor for gathering user touch input, a temperature sensor, apressure sensor, an ambient light sensor, a microphone or other soundsensor that gathers ambient noise measurements and user input such asvoice commands, sensors for gathering data on device position and motionsuch as inertial measurement units that include accelerometers,compasses, and/or gyroscopes, and/or other sensors.

Input-output devices 52 may also include other components 54 such asbuttons, joysticks, scrolling wheels, touch pads, key pads, keyboards,speakers, tone generators, vibrators, cameras, light-emitting diodes andother status indicators, data ports, etc. A user can control theoperation of device 10 by supplying user input commands throughinput-output devices 52 and may receive status information and otheroutput from device 10 using the output resources of input-output devices52.

Control circuitry 50 may be used to run software on device 10 such asoperating system code and applications. During operation of device 10,the software running on control circuitry 50 may display images ondisplay 14 (e.g., video, still images such as text, alphanumeric labels,photographs, icons, other graphics, etc.) using an array of pixels indisplay 14.

As shown in FIG. 3 , device 10 may be folded (bent by 180° or othersuitable amount) about bend axis 22 so that display 14 is visible fromthe outside of device 10 in its folded state. FIG. 4 shows how device 10may be folded about bend axis 22 so that display 14 is protected withinthe interior of device 10. Device 10 may have flexible structures (e.g.,a hinge) to allow outward bending of the type shown in FIG. 3 , to allowinward bending of the type shown in FIG. 4 , or to allow bending of boththe type shown in FIG. 3 and the type shown in FIG. 4 . Configurationsin which device 10 is flexed by different amounts (e.g., more than 180°or less than 180°) may also be used.

Display 14 may have a rectangular shape (i.e., display 14 may have arectangular footprint and a rectangular peripheral edge that runs aroundthe rectangular footprint) or may have other suitable shapes. A top viewof circuitry in an illustrative display with a rectangular shape isshown in FIG. 5 . As shown in FIG. 5 , display 14 may have an array ofpixels 42 formed on substrate 36. Substrate 36 may be formed from glass,metal, plastic, ceramic, or other substrate materials. Pixels 42 mayreceive data signals over signal paths such as data lines D and mayreceive one or more control signals over control signal paths such ashorizontal control lines G (sometimes referred to as gate lines, scanlines, emission control lines, etc.). There may be any suitable numberof rows and columns of pixels 42 in display 14 (e.g., tens or more,hundreds or more, or thousands or more). Each pixel 42 may have alight-emitting diode 26 that emits light 44 under the control of a pixelcircuit formed from thin-film transistor circuitry such as thin-filmtransistors 28 and thin-film capacitors). Thin-film transistors 28 maybe polysilicon thin-film transistors, semiconducting-oxide thin-filmtransistors such as indium gallium zinc oxide transistors, or thin-filmtransistors formed from other semiconductors. Pixels 42 may containlight-emitting diodes of different colors (e.g., red, green, and bluediodes for red, green, and blue pixels, respectively) to provide display14 with the ability to display color images.

Display driver circuitry may be used to control the operation of pixels42. The display driver circuitry may be formed from integrated circuits,thin-film transistor circuits, or other suitable circuitry. Displaydriver circuitry 30 of FIG. 2 may contain communications circuitry forcommunicating with system control circuitry such as control circuitry 50of FIG. 2 over path 32. Path 32 may be formed from traces on a flexibleprinted circuit or other cable. During operation, the control circuitry(e.g., control circuitry 50 of FIG. 2 ) may supply circuitry 30 withinformation on images to be displayed on display 14.

To display the images on pixels 42, display driver circuitry 30 maysupply image data to data lines D while issuing clock signals and othercontrol signals to supporting display driver circuitry such as gatedriver circuitry 34 over path 38. If desired, circuitry 30 may alsosupply clock signals and other control signals to gate driver circuitryon an opposing edge of display 14 or may use display driver circuitrywith other layouts. The configuration of FIG. 5 is illustrative.

Gate driver circuitry 34 (sometimes referred to as horizontal controlline control circuitry) may be implemented as part of an integratedcircuit and/or may be implemented using thin-film transistor circuitry.Gate lines G (sometimes referred to as horizontal control lines) indisplay 14 may carry gate line signals (sometimes referred to as scanline signals, emission enable control signals, etc.) for controlling thepixels of each row. There may be any suitable number of control signalsper row of pixels 42 (e.g., one or more, two or more, three or more,four or more, etc.).

Display 14 may have an outermost layer formed from clear glass,transparent plastic, sapphire, or other transparent materials that serveas a protective layer for thin-film transistor circuitry and otherdisplay structures. The outer display layer may sometimes be referred toas a display cover layer. In some configurations for display 14, theoutermost layer of the display may serve both as a protective layer(display cover layer) and as a substrate for display structures (touchsensors electrodes, color filter elements, thin-film transistors, etc.).In other configurations, the display cover layer is free of circuitryand serves solely as a protective layer for underlying displaystructures (e.g., one or more underlying display panels).

As shown in FIG. 6 , a display cover layer for display 14 (i.e., displaycover layer 24) may have rigid portions such as rigid portions 24A andflexible portions such as flexible portion 24B. Rigid portions 24A may,for example, be rigid planar layers. Configurations in which portions24A have non-planar shapes and/or are formed from flexible structuresmay also be used. Between rigid planar portions 24A of display coverlayer 24, display cover layer 24 may have flexible portion 24B. Portion24B may bend about bend axis 22 to allow display 14 to bend as housing12 is bent about hinge 20.

In the example of FIG. 6 , flexible portion 24B of display cover layer24 aligns with flexible region 14B of display 14 (e.g., the region ofdisplay 14 that bends about bend axis 22). This is, however, merelyillustrative. If desired, display cover layer 24 may include flexibleregions 24B in rigid areas 14A of display 14 (e.g., in areas of display14 that do not bend, that are prevented from being bent, or that areotherwise less flexible than regions 14B).

In some cases, display cover layer 24 may be formed from a singletransparent layer formed from glass, plastic, sapphire, or anothertransparent material. In other arrangements, however, display coverlayer 24 may include more than one layer of material. For example, inaddition to a transparent dielectric layer, the display cover layer mayinclude a layer with self-healing properties.

During operation of an electronic device, the display cover layer forthe electronic device may be scratched or dented. To improve theaesthetics of electronic device, it may be desirable for the presence ofscratches and dents to be minimized. To help mitigate the number ofdents, scratches, or other imperfections in a display cover layer, thedisplay cover layer may include a layer with self-healing properties(e.g., a layer of self-healing material). For example, a self-healingcoating may be formed on a transparent dielectric layer. Theself-healing coating may be dented or scratched during operation of theelectronic device. However, because of the self-healing properties ofthe self-healing coating, the self-healing coating may return to itsoriginal shape and the dents and scratches may be removed. Theself-healing may occur without prompting (e.g., when the self-healingcoating is dented, the material of the coating may fill the dent evenwithout intervention from an external influence). Alternatively, theself-healing may be initiated or expedited by externally applied heat,light, electric current, or other type of external stimulus.

FIG. 7 is a cross-sectional side view of a display that includes adisplay cover layer with a layer of self-healing material. As shown inFIG. 7 , display cover layer 24 includes a transparent dielectric layer62. The display cover layer may cover underlying display layers 66 inthe display (e.g., substrate 36 and other layers that form thelight-emitting diodes and control circuitry of FIG. 5 ). Transparentdielectric layer 62 may be formed from a transparent layer of plastic,glass, sapphire, or any other desired material. Display cover layer 24also includes a layer of self-healing material 64. The layer ofself-healing material 64 may, for example, form an exterior surface ofthe display cover layer (meaning that the self-healing layer 64 isexposed to the exterior of the electronic device). By formingself-healing material at the exterior of the display cover glass, theself-healing material will be exposed during operation of the device.However, as previously mentioned, the self-healing material may be ableto automatically repair any damage to itself. The self-healing materialmay automatically repair any damage to itself without externalintervention or the self-healing process may be initiated by heat,light, or another external stimulus. The self-healing layer 64 may beformed from polymer or any other desired material having self-healingproperties.

To ensure that flexible portion 24B of display cover layer 24 hassufficient flexibility, the transparent dielectric layer 62 may have areduced thickness in flexible portion 24B. As shown in FIG. 7 ,transparent dielectric layer 62 has a thickness 68 in rigid portions 24Aof the display cover layer and a thickness 70 in flexible portion 24B ofthe display cover layer. Thickness 70 is less than thickness 68.Thinning the transparent dielectric layer in this way may increaseflexibility in the flexible region.

Self-healing layer 64 may be elastic to allow for sufficient flexibilityin the flexible portion of the display cover layer. Self-healing layer64 may be more elastic than transparent dielectric layer 62.Self-healing layer 64 is thicker in flexible region 24B than in therigid regions 24A of the display cover layer. As previously mentioned,flexible region 24B may bend about bend axis 22 to allow display 14 tobend as housing 12 is bent about hinge 20. Self-healing layer 64 maytherefore both provide a self-healing coating across the display coverlayer for improved aesthetic and mechanical display cover layerperformance and provide increased flexibility to allow bending in thedisplay cover layer.

In FIG. 7 , display cover layer 24 is depicted as having a singletransparent dielectric layer 62 that has a reduced thickness portion inflexible region 24B of the display cover layer. This example, however,is merely illustrative. Display cover layer 24 may instead includemultiple layers of transparent dielectric material that are attachedtogether. An example of this type is shown in FIG. 8 .

FIG. 8 is a cross-sectional side view of an illustrative display havinga display cover layer formed from multiple layers of transparentdielectric material. As shown in FIG. 8 , display cover layer 24includes transparent dielectric layers 62-1, 62-2, and 62-3. The displaycover layer may cover underlying display layers 66 in the display (e.g.,substrate 36 and other layers that form the light-emitting diodes andcontrol circuitry of FIG. 5 ). Transparent dielectric layers 62-1, 62-2,and 62-3 may be formed from transparent layers of plastic, glass,sapphire, or any other desired material.

Display cover layer 24 also includes a layer of self-healing material64. The layer of self-healing material 64 may, for example, form aportion of an exterior surface of the display cover layer in flexibleregion 24B of the display cover layer. To ensure that flexible portion24B of display cover layer 24 has sufficient flexibility, the cumulativethickness of the transparent dielectric layers is reduced in flexibleportion 24B. As shown in FIG. 8 , transparent dielectric layers 62-1 and62-2 are formed on first and second opposing sides of self-healingmaterial 64. An adhesive layer 72 attaches the transparent dielectriclayers 62-1 and 62-2 to transparent dielectric layer 62-3. Adhesivelayer 72 may be formed from pressure sensitive adhesive or a liquidadhesive. Adhesive layer 72 may be an optically clear adhesive (OCA).

Transparent dielectric layer 62-3 may be thinner than transparentdielectric layers 62-1 and 62-2. In this way, the shape of the singletransparent dielectric layer 62 in FIG. 7 is approximated with multipletransparent dielectric layers in FIG. 8 . Using multiple transparentdielectric layers attached together to produce a reduced transparentdielectric layer thickness area (as in FIG. 8 ) may result in reducedmanufacturing time and costs compared to using a single transparentdielectric layer with a thinned region to produce a reduced transparentdielectric layer thickness area (as in FIG. 7 ).

Self-healing layer 64 may be elastic to allow for sufficient flexibilityin the flexible portion of the display cover layer. Self-healing layer64 may be more elastic than transparent dielectric layers 62-1, 62-2,and 62-3. As previously mentioned, flexible region 24B may bend aboutbend axis 22 to allow display 14 to bend as housing 12 is bent abouthinge 20. Self-healing layer 64 may therefore both provide aself-healing portion of the display cover layer and provide increasedflexibility to allow bending in the display cover layer.

FIG. 9 is a cross-sectional side view of an illustrative display havinga display cover layer with an elastomer formed in a flexible region ofthe display cover layer. As shown in FIG. 9 , similar to as in FIG. 8display cover layer 24 includes transparent dielectric layers 62-1,62-2, and 62-3. The display cover layer may cover underlying displaylayers 66 in the display (e.g., substrate 36 and other layers that formthe light-emitting diodes and control circuitry of FIG. 5 ). Transparentdielectric layers 62-1, 62-2, and 62-3 may be formed from transparentlayers of plastic, glass, sapphire, or any other desired material. Thenomenclature of referring to transparent dielectric layers 62-1 and 62-2as separate dielectric layers is merely illustrative. In some cases,these transparent dielectric layers may be referred to as a singletransparent dielectric layer with an opening (e.g., that is filled withelastomer and/or self-healing material).

Display cover layer 24 also includes a layer of self-healing material64. The layer of self-healing material 64 may, for example, form aportion of an exterior surface of the display cover layer in flexibleregion 24B of the display cover layer. To ensure that flexible portion24B of display cover layer 24 has sufficient flexibility, an elastomerlayer 74 is also formed in flexible portion 24B of the display coverlayer. Elastomer layer 74 may be more elastic than self-healing layer64. Therefore, the presence of elastomer layer 74 may increase theflexibility of flexible region 24B (compared to when only theself-healing layer 64 is present in flexible region 24B as in FIG. 8 ).Elastomer layer 74 may be formed from any desired material (e.g., anatural or synthetic polymer). Elastomer layer 74 may have a Young'smodulus that is lower than the Young's modulus of self-healing layer 64and self-healing layer 64 may have a Young's modulus that is lower thanthe Young's modulus of the transparent dielectric layers.

Adhesive layer 72 attaches the transparent dielectric layers 62-1 and62-2 as well as elastomer layer 74 to transparent dielectric layer 62-3.Adhesive layer 72 may be formed from pressure sensitive adhesive or aliquid adhesive. Adhesive layer 72 may be an optically clear adhesive(OCA). As previously mentioned, flexible region 24B may bend about bendaxis 22 to allow display 14 to bend as housing 12 is bent about hinge20.

FIG. 10 is a cross-sectional side view of an illustrative display inwhich the cover layer includes a self-healing coating across the displaycover layer and an elastomer layer in the flexible region of the displaycover layer. As shown in FIG. 10 , display cover layer 24 includestransparent dielectric layers 62-1, 62-2, and 62-3. The display coverlayer may cover underlying display layers 66 in the display (e.g.,substrate 36 and other layers that form the light-emitting diodes andcontrol circuitry of FIG. 5 ). Transparent dielectric layers 62-1, 62-2,and 62-3 may be formed from transparent layers of plastic, glass,sapphire, or any other desired material.

Display cover layer 24 also includes a layer of self-healing material64. The layer of self-healing material 64 may, for example, form anexterior surface of the display cover layer (meaning that theself-healing layer 64 is exposed to the exterior of the electronicdevice). The self-healing material may extend across the entire exteriorsurface of the display cover layer. By forming self-healing material atthe exterior of the display cover glass, the self-healing material willbe exposed during operation of the device. However, as previouslymentioned, the self-healing material be able to automatically repair anydamage to itself. The self-healing material may automatically repair anydamage to itself without external intervention or the self-healingprocess may be initiated by heat, light, or another external stimulus.The self-healing layer 64 may be formed from polymer or any otherdesired material having self-healing properties.

To ensure that flexible portion 24B of display cover layer 24 hassufficient flexibility, an elastomer layer 74 is also formed in flexibleportion 24B of the display cover layer. Elastomer layer 74 may be moreelastic than self-healing layer 64. Therefore, the presence of elastomerlayer 74 may increase the flexibility of flexible region 24B. Elastomerlayer 74 may be formed from any desired material (e.g., a natural orsynthetic polymer). Elastomer layer 74 may have a Young's modulus thatis lower than the Young's modulus of self-healing layer 64 andself-healing layer 64 may have a Young's modulus that is lower than theYoung's modulus of the transparent dielectric layers.

Adhesive layer 72 attaches the transparent dielectric layers 62-1 and62-2 as well as elastomer layer 74 to transparent dielectric layer 62-3.Adhesive layer 72 may be formed from pressure sensitive adhesive or aliquid adhesive. Adhesive layer 72 may be an optically clear adhesive(OCA). As previously mentioned, flexible region 24B may bend about bendaxis 22 to allow display 14 to bend as housing 12 is bent about hinge20.

FIG. 11 is a cross-sectional side view of an illustrative display inwhich the display cover layer includes a self-healing coating across thedisplay cover layer and a heating layer that heats the self-healingcoating. As shown in FIG. 11 , display cover layer 24 includestransparent dielectric layers 62-1, 62-2, and 62-3. The display coverlayer may cover underlying display layers 66 in the display (e.g.,substrate 36 and other layers that form the light-emitting diodes andcontrol circuitry of FIG. 5 ). Transparent dielectric layers 62-1, 62-2,and 62-3 may be formed from transparent layers of plastic, glass,sapphire, or any other desired material.

Display cover layer 24 also includes a layer of self-healing material64. The layer of self-healing material 64 may, for example, form anexterior surface of the display cover layer (meaning that theself-healing layer 64 is exposed to the exterior of the electronicdevice). By forming self-healing material at the exterior of the displaycover glass, the self-healing material will be exposed during operationof the device. However, as previously mentioned, the self-healingmaterial be able to automatically repair any damage to itself. Theself-healing process of the self-healing material may be initiated orexpedited by heat. Therefore, a heating element may be included in thedisplay cover layer to heat the self-healing layer.

As shown in FIG. 11 , heating layer 76 may be formed between transparentdielectric layer 62-3 and adhesive layer 72. The heating layer may be aresistive heater in which the passage of electric current through aconductor produces heat. In other words, the heating layer may includeconductive traces (e.g., on a surface of transparent dielectric layer62-3) that receive an applied electric current. For example, a first endof the conductive traces may be coupled to a positive power supplyterminal and a second end of the conductive traces may be coupled to aground power supply terminal. The conductive traces of heating layer 76may follow a meandering path (e.g., the conductive traces may have aseries of bends to extend the length of the traces and accordinglyincrease the resistance of the conductive traces). The conductive tracesof heating layer 76 may be formed from a transparent conductive materialsuch as indium tin oxide (ITO) or silver nanowire.

To ensure that flexible portion 24B of display cover layer 24 hassufficient flexibility, an elastomer layer 74 is also formed in flexibleportion 24B of the display cover layer. Elastomer layer 74 may be moreelastic than self-healing layer 64. Therefore, the presence of elastomerlayer 74 may increase the flexibility of flexible region 24B. Elastomerlayer 74 may be formed from any desired material (e.g., a natural orsynthetic polymer). Elastomer layer 74 may have a Young's modulus thatis lower than the Young's modulus of self-healing layer 64 andself-healing layer 64 may have a Young's modulus that is lower than theYoung's modulus of the transparent dielectric layers.

Adhesive layer 72 attaches the transparent dielectric layers 62-1 and62-2 as well as elastomer layer 74 to heating layer 76 and transparentdielectric layer 62-3. Adhesive layer 72 may be formed from pressuresensitive adhesive or a liquid adhesive. Adhesive layer 72 may be anoptically clear adhesive (OCA). As previously mentioned, flexible region24B may bend about bend axis 22 to allow display 14 to bend as housing12 is bent about hinge 20.

The heating layer may selectively be heated in order to stimulate theself-healing of self-healing material 64. Control circuitry within theelectronic device (e.g., control circuitry 50 in FIG. 2 ) may be used toprovide signals (e.g., an electric current) to heating layer 76 togenerate heat with the heating layer. The control circuitry may heat theheating layer in response to user input. For example, a user of theelectronic device may provide instructions to the electronic deviceusing one or more of the input-output devices in the electronic device(e.g., input-output devices 52 in FIG. 2 ). The user may, for example,use the input-output devices to provide instructions for immediatelygenerating heat with the heating layer for the self-healing process.Alternatively, the user may schedule a time or times at which theheating layer will generate heat for the self-healing process.

In other arrangements, control circuitry in the electronic device maydetermine when to use the heating layer to generate heat without userinput. For example, the control circuitry may provide signals to theheating layer to generate heat after a predetermined amount ofelectronic device usage or according to a predetermined schedule. Thecontrol circuitry may analyze the historical device usage and providesignals to the heating layer to generate heat based on the historicaldevice usage. In other embodiments, the control circuitry may providesignals to the heating layer to generate heat when the electronic deviceis being charged (e.g., when the electronic device receives wireless orwired power to provide power for operating the electronic device or torecharge the electronic device battery) or in other predetermined usagescenarios.

Control circuitry in the electronic device may monitor the temperatureof the heating layer to ensure that the temperature of the electronicdevice does not exceed certain temperature thresholds. For example, theelectronic device may have a maximum allowable temperature above whichthe internal components of the electronic device may be compromised. Theelectronic device may have a safety temperature above which theelectronic device may not be safe for a user to touch. The controlcircuitry may stop generating heat with the heating layer if any desiredtemperature limit is exceeded.

In general, it may be desirable for the components of display coverlayer 64 to have similar indices of refraction in order to avoiddifferent portions of the display cover layer having differentappearances. The materials used to form the display cover layer may beselected to have similar indices of refraction. For example, elastomer74 may have a similar index of refraction as transparent dielectriclayers 62-1 and 62-2 (e.g., the two indices of refraction may be within0.2, within 0.1, within 0.05, without 0.03, within 0.01, etc.).Elastomer 74 may have a similar index of refraction as self-healinglayer 64 (e.g., the two indices of refraction may be within 0.2, within0.1, within 0.05, without 0.03, within 0.01, etc.). Transparentdielectric layers 62-1 and 62-2 may have a similar index of refractionas self-healing layer 64 (e.g., the two indices of refraction may bewithin 0.2, within 0.1, within 0.05, without 0.03, within 0.01, etc.).Elastomer 74 may have a similar index of refraction as adhesive layer 72(e.g., the two indices of refraction may be within 0.2, within 0.1,within 0.05, without 0.03, within 0.01, etc.).

These examples are merely illustrative. In general, all of the materialswithin the display cover layer may be selected to have similar indicesof refraction when possible. In some cases, however, there may bedifferences between the indices of refraction of materials within thedisplay cover layer. Index-matching layers may be incorporated in thedisplay cover layer to mitigate visible artifacts caused by materialshaving different indices of refraction. FIG. 12 is a cross-sectionalside view of a display having a display cover layer with the samearrangement as in FIG. 11 . However, in addition to the components shownand discussed in connection with FIG. 11 , the display cover layer ofFIG. 12 includes index-of-refraction-matching layers 80-1 and 80-2(sometimes referred to simply as index-matching layers 80-1 and 80-2).

As shown in FIG. 12 , index-matching layer 80-1 is interposed betweenadhesive 72 and heating layer 76. Index-matching layer 80-1 may have anindex of refraction that is between the index of refraction of adhesive72 and the index of refraction of heating layer 76. Index-matching layer80-2 is interposed between heating layer 76 and transparent dielectriclayer 62-3. Index-matching layer 80-2 may have an index of refractionthat is between the index of refraction of heating layer 76 and theindex of refraction of transparent dielectric layer 62-3. The twoindex-matching layers depicted in FIG. 12 are merely illustrative. Ingeneral, index-matching layers may be incorporated between any twoadjacent layers within display cover layer 24.

The position of heating layer 76 in FIG. 11 is merely illustrative. Ingeneral, the heating layer for heating the self-healing material may beincorporated at any desired position within the display. FIG. 13 is across-sectional side view of a display having a display cover layer withthe same arrangement as in FIG. 11 , except for the position of theheating layer.

As shown in FIG. 13 , instead of positioning the heating layer betweenadhesive layer 72 and transparent dielectric layer 62-3 (as in FIG. 11), the heating layer 76 (sometimes referred to as heat-generating layer76) is positioned between self-healing coating 64 and transparentdielectric layers 62-1 and 62-2. Positioning the heating layer directlyadjacent to the self-healing layer in this way may result in more of theheat generated by the heating layer reaching the self-healing layer.This may result in improved self-healing performance in the self-healingmaterial. However, positioning the heating layer immediately adjacentthe self-healing material may require the heating layer to be veryflexible. To optimize the flexibility of the display cover layer, theheating layer may be positioned further from the self-healing material(e.g., as in FIG. 11 ).

The examples of FIGS. 9-13 of elastomer layer 74 being formed in theflexible region of the display cover layer are merely illustrative. Ifdesired, a flexible material of another type may replace elastomer layer74 in FIGS. 9-13 . For example, a plurality of layers of thin plastic(attached together with adhesive layers) may replace elastomer layer 74.

The examples of transparent dielectric layers used in FIGS. 7-13 arealso illustrative. It should be understood that, in general, anycombination of transparent dielectric layers having uniform thicknessesand transparent dielectric layers having varying thicknesses may be usedto form the display cover layer.

In FIGS. 11-13 , examples are shown where a transparent conductor isincluded to form a heating element for heating the self-healing layer ofthe display cover layer. This type of arrangement may be used when theself-healing process of the self-healing material is initiated orexpedited by heat. However, the self-healing material may instead bepromoted by a different stimulus such as exposure to light or electriccurrent.

In embodiments where the self-healing process is initiated or expeditedby exposure to light, any desired light source may be used to providethe exposure to light. If exposure to visible light is a stimulus forthe self-healing process, light emitted by the flexible display may beused to provide the stimulus for the self-healing process.Alternatively, a separate light source in the electronic device may beused to provide light as a stimulus for the self-healing process. Insome cases, exposure to ultraviolet light may be stimulus for theself-healing process. An ultraviolet light source may be included in theelectronic device to provide the ultraviolet light or ambientultraviolet light may naturally stimulate the self-healing processwithout external intervention.

In yet another possible arrangement, the self-healing process may beinitiated or expedited in response to an electric current. Controlcircuitry may be configured to apply an electric current to theself-healing material. For example, the self-healing material may becoupled to a positive power supply terminal and a ground power supplyterminal.

Regardless of the type of stimulus used to initiate and/or expedite theself-healing process in the self-healing material, the control circuitrymay provide the stimulus in a number of possible ways. The controlcircuitry may provide the stimulus in response to user input. Forexample, a user of the electronic device may provide instructions to theelectronic device using one or more of the input-output devices in theelectronic device (e.g., input-output devices 52 in FIG. 2 ). The usermay, for example, use the input-output devices to provide instructionsfor immediately starting for the self-healing process. Alternatively,the user may schedule a time or times at which the self-healing processwill be initiated by the stimulus. In other arrangements, the controlcircuitry in the electronic device may determine when to provide thestimulus. For example, the control circuitry may provide the stimulusafter a predetermined amount of electronic device usage or according toa predetermined schedule. The control circuitry may analyze the deviceusage and provide the stimulus based on the device usage. In otherembodiments, the control circuitry may provide the stimulus whenever theelectronic device is being charged (e.g., when the electronic devicereceives wireless or wired power to provide power for operating theelectronic device or to recharge the electronic device battery) or inother predetermined usage scenarios.

In FIGS. 8-13 , examples are shown where separate pieces of transparentdielectric material are used instead of a single, thinned layer oftransparent dielectric (as in FIG. 7 ). In the examples of FIGS. 8-13 ,materials such as elastomer 74 and/or self-healing material 64 fill agap between transparent dielectric layers 62-1 and 62-2. There is also atransparent dielectric layer 62-3 formed under layers 62-1 and 62-2 thatis uninterrupted in flexible portion 24B. This example of an arrangementfor multiple transparent dielectric layers is merely illustrative. Inyet another possible arrangement, a transparent dielectric layer mayhave a plurality of slits in flexible portion 24B to promote bending.

FIG. 14 is a cross-sectional side view of an illustrative display havinga display cover layer formed from a layer of transparent dielectricmaterial with slits. As shown in FIG. 14 , display cover layer 24includes transparent dielectric layers 62-1 and 62-2. The display coverlayer may cover underlying display layers 66 in the display (e.g.,substrate 36 and other layers that form the light-emitting diodes andcontrol circuitry of FIG. 5 ). Transparent dielectric layers 62-1 and62-2 may be formed from transparent layers of plastic, glass, sapphire,or any other desired material.

Transparent dielectric layer 62-2 may have a plurality of slits 82(which may sometimes be referred to as holes, recesses, grooves,openings, etc.) in flexible portion 24B to increase the flexibility ofthe display cover layer. Because transparent dielectric layer 62-2 has apattern of slits in the flexible portion of the display cover glass,transparent dielectric layer 62-2 may sometimes be referred to as apatterned transparent dielectric layer or a patterned glass layer.Transparent dielectric layer 62-2 is covered by transparent dielectriclayer 62-1. The thickness of dielectric layer 62-2 may be greater thanthe thickness of dielectric layer 62-1 (e.g., at least two timesgreater, at least three times greater, at least five times greater, atleast ten times greater, at least twenty times greater, etc.). With thisarrangement, the dielectric cover layer may have flexibility in flexibleregion 24B while maintaining sufficient structural integrity in theadjacent rigid portions 24A.

Index-matching layers may be incorporated in the display cover layer tomitigate visible artifacts caused by materials having different indicesof refraction. As shown in FIG. 14 , the display cover layer 24 includesindex-of-refraction-matching layers 86-1 and 86-2 (sometimes referred tosimply as index-matching layers 86-1 and 86-2). Index-matching layer86-1 is interposed between patterned transparent dielectric layer 62-2and display layers 66. Index-matching layer 86-1 may have an index ofrefraction that is between the index of refraction of transparentdielectric layer 62-2 and the index of refraction of display layers 66and/or may have an index of refraction that is approximately equal to(e.g., within 5% of) the index of refraction of transparent dielectriclayer 62-2. Index-matching layer 86-2 may fill the slits 82 intransparent dielectric layer 62-2. Index-matching layer 86-2 may have anindex of refraction that is close to or equal to the index of refractionof transparent dielectric layer 62-2 (e.g., within 10% of, within 5% of,within 1% of, within 0.1% of, etc.) to avoid the slits being visible tothe user.

The nomenclature of FIG. 14 , with index-matching layers 86-1 and 86-2receiving separate labels, is merely illustrative. In one illustrativearrangement, the same material may be used to form both index-matchinglayers 86-1 and 86-2. In this type of arrangement, the index-matchinglayer may be considered to be a single, integral index-matching layerwith a first portion between dielectric layer 62-2 and display layers 66and a second portion that fills the slits in dielectric layer 62-2.

The index-matching layers may also increase the flexibility of flexibleportion 24B of the display cover layer. The index-matching layers may bemore elastic than dielectric layer 62-2 (and optionally more elasticthan self-healing layer 64). Index-matching layers 86-1 and 86-2 may beformed from any desired material (e.g., a natural or synthetic polymer).Index-matching layers 86-1 and 86-2 may have a Young's modulus that islower than the Young's modulus of self-healing layer 64 and/or thetransparent dielectric layers 62. Because the index-matching layers mayhave elastomeric properties and may increase the flexibility of thedisplay cover layer, the index-matching layers may sometimes also bereferred to as elastomeric layers.

Transparent dielectric layers 62-1 and 62-2 may both be glass layers.The glass layers may be coupled together with glass-to-glass welds 84.The glass-to-glass welds may be formed using laser welding that heatsthe glass layers and causes the glass layers to fuse together at welds84. This example is merely illustrative, and welds 84 may be formedusing any desired techniques.

Display cover layer 24 may also include a layer of self-healing material64, similar to as previously described in connection with FIGS. 8-13 .In FIG. 14 , the self-healing material is depicted as being formed overthe entire display cover layer. This example is merely illustrative. Ifdesired, the self-healing material 64 may be patterned (e.g., onlyformed in flexible portion 24B of the display cover layer). Theself-healing material 64 from FIG. 14 may also optionally be omittedfrom the display cover layer.

The example in FIG. 14 of transparent dielectric layers 62-1 and 62-2being attached together by welds 84 is merely illustrative. If desired,an adhesive layer may be used to attach transparent dielectric layer62-1 to transparent dielectric layer 62-2. FIG. 15 is a cross-sectionalside view of an illustrative display cover layer with an adhesive layer88 between transparent dielectric layer 62-1 and transparent dielectriclayer 62-2. Adhesive layer 88 may attach transparent dielectric layer62-1 to transparent dielectric layer 62-2. Adhesive layer 88 may beformed from any desired material. In some cases, the adhesive layer maybe an epoxy that includes polymer material. In other possiblearrangements, adhesive layer 88 may be formed from a pressure sensitiveadhesive (PSA), a liquid optically clear adhesive (LOCA), etc.

In FIGS. 14 and 15 , slits 82 extend entirely through transparentdielectric layer 62-2. The slits 82 may sometimes be referred to asthrough-holes that extend from an upper surface of the transparentdielectric layer to a lower surface of the transparent dielectric layer.This example is merely illustrative. If desired, the slits may extendonly partially into the transparent dielectric layer 62-2 (e.g., apartial through-hole that does not reach the lower surface of thetransparent dielectric layer).

FIG. 16 is a cross-sectional side view of an illustrative display coverlayer with partial slits in a transparent dielectric layer. As shown inFIG. 16 , slits 82 may extend only partially through transparentdielectric layer 62-2. The separate slits may merge into a unitaryopening 90 at a lower part of the flexible portion of transparentdielectric layer 62-2. Index-matching layer 86 may have a first portionthat is formed between transparent dielectric layer 62-2 and displaylayers 66, a second portion that fills the unitary opening 90 intransparent dielectric layer 62-2, and a third portion that fills theslits 82 in transparent dielectric layer 62-2. These different portionsof the index-matching layer may be formed from the same material or fromdifferent materials (similar to as discussed in connection with FIG. 14).

FIG. 16 depicts transparent dielectric layers 62-1 and 62-2 as beingattached together using welds 84 (similar to as in FIG. 14 ). However,it should be understood that the dielectric layers may instead beattached using an adhesive layer (similar to as in FIG. 15 ).

FIG. 17 is a cross-sectional side view of a display cover layer showinghow three transparent dielectric layers may be used instead of the twotransparent dielectric layers of FIG. 16 . As shown in FIG. 17 ,transparent dielectric layer 62-3 may have a single opening 90 inflexible portion 24B of the display cover layer. Transparent dielectriclayer 62-2 may have slits 82 in flexible portion 24B of the displaycover layer. Transparent dielectric layer 62-1 may cover the entiredisplay. Dielectric layer 62-1 may be thinner than both dielectric layer62-2 and dielectric layer 62-3 (e.g., by a factor of more than two, by afactor of more than three, by a factor of more than five, by a factor ofmore than ten, by a factor of more than twenty, etc.). Transparentdielectric layers 62-1, 62-2, and 62-3 may be formed from transparentlayers of plastic, glass, sapphire, or any other desired material.

A first index-matching layer 86-1 may be interposed between transparentdielectric layer 62-3 and display layers 66. A second index-matchinglayer 86-2 may fill opening 90 in transparent dielectric layer 62-3. Athird index-matching layer 86-3 may fill slits 82 in transparentdielectric layer 62-2. Similar to as discussed in connection with FIG.14 , the index-matching layers may be formed from the same material andtherefore may be sometimes referred to as a single index-matching layerwith various portions. It should be noted that in any of FIGS. 14-17 ,self-healing layer 64 may optionally be omitted or patterned.

FIG. 17 depicts transparent dielectric layers 62-1 and 62-2 as beingattached together using welds 84 (similar to as in FIG. 14 ). However,it should be understood that the dielectric layers may instead beattached using an adhesive layer (similar to as in FIG. 15 ). FIG. 17also depicts transparent dielectric layers 62-2 and 62-3 as beingattached together using welds 84 (similar to as in FIG. 14 ). However,it should be understood that the dielectric layers may instead beattached using an adhesive layer (similar to as in FIG. 15 ). Ingeneral, any interface between adjacent transparent dielectric layersmay include an adhesive layer for attaching the two transparentdielectric layers or may include welds for attaching the two transparentdielectric layers.

FIG. 18 is a top view showing an illustrative arrangement for slits 82in the flexible region 24B of display cover layer 24 (e.g., as in any ofFIGS. 14-17 ). As shown in FIG. 18 , each slit may be an elongated slitthat extends along an axis that is parallel to the bend axis of flexibleportion 24B (e.g., bend axis 22 in FIG. 1 ). The slit pattern depictedin FIG. 18 is merely illustrative. The openings may not be elongated(e.g., circular holes may be used instead of elongated slits). The slitsmay include zig-zags (e.g., portions that are angled relative to thebend-axis). In general, any desired number and shapes of openings may beformed in the transparent dielectric layer 62-2.

FIGS. 7-18 depict a display cover layer for a display that bends along asingle bend-axis (as depicted in FIG. 1 , for example). However, itshould be understood that the flexible display cover layer regions shownand described in FIGS. 7-18 may be applied to a display that bends alongany desired number of bend-axes. The display cover layer may bend alongone, two, or more than two bend-axes. The display cover layer may have aflexible region along each bend-axis. In one possible arrangement, theentire display cover layer may be flexible.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device, comprising: a housing thatbends about a bend axis; and a display in the housing that bends aboutthe bend axis, wherein the display comprises a display cover layerhaving first and second rigid portions and a flexible portion interposedbetween the first and second rigid portions, wherein the first andsecond rigid portions comprise first and second respective transparentdielectric layers, wherein the flexible portion comprises a layer ofelastomer that is interposed between the first and second transparentdielectric layers, and wherein the display cover layer includes apolymer layer that is formed over the layer of elastomer and the firstand second transparent dielectric layers.
 2. The electronic devicedefined in claim 1, wherein the polymer layer is a self-healing polymerlayer and wherein the display cover layer further comprises an adhesivelayer that attaches the first and second transparent dielectric layersand the layer of elastomer to a third transparent dielectric layer. 3.The electronic device defined in claim 2, wherein the adhesive layer isan optically clear adhesive layer.
 4. The electronic device defined inclaim 2, wherein the display cover layer further comprises a transparentconductor layer used to generate heat to promote self-healing in theself-healing polymer layer.
 5. The electronic device defined in claim 4,wherein the transparent conductor layer is interposed between theadhesive layer and the third transparent dielectric layer.
 6. Theelectronic device defined in claim 4, wherein the transparent conductorlayer is interposed between the first and second transparent dielectriclayers and the self-healing polymer layer and wherein the transparentconductor layer is interposed between the layer of elastomer and theself-healing polymer layer.
 7. The electronic device defined in claim 1,wherein the polymer layer extends across an entire exterior surface ofthe display cover layer.
 8. The electronic device defined in claim 1,wherein the elastomer has a lower Young's modulus than the polymerlayer.
 9. An electronic device, comprising: a housing that bends about abend axis; and a display in the housing that bends about the bend axis,wherein the display comprises a display cover layer having first andsecond rigid portions and a flexible portion interposed between thefirst and second rigid portions, wherein the first and second rigidportions comprise first and second respective transparent dielectriclayers, wherein the flexible portion comprises a first layer that isinterposed between the first and second transparent dielectric layers,wherein the display cover layer includes a second layer that is formedover the first layer and the first and second transparent dielectriclayers, and wherein the first layer has a lower Young's modulus than thesecond layer.
 10. The electronic device defined in claim 9, wherein thesecond layer is a self-healing polymer layer and wherein the displaycover layer further comprises an adhesive layer that attaches the firstand second transparent dielectric layers and the first layer to a thirdtransparent dielectric layer.
 11. The electronic device defined in claim10, wherein the adhesive layer is an optically clear adhesive layer. 12.The electronic device defined in claim 9, wherein the second layerextends across an entire exterior surface of the display cover layer.13. The electronic device defined in claim 9, wherein the first layercomprises elastomer.
 14. The electronic device defined in claim 9,wherein the second layer has a lower Young's modulus than the first andsecond transparent dielectric layers.
 15. An electronic device,comprising: a housing; and a flexible display in the housing having abending region that bends about a bend axis, wherein the flexibledisplay includes display layers configured to emit light and a displaycover layer, wherein the display cover layer covers the display layers,and wherein the display cover layer comprises: a first transparentdielectric layer having a plurality of slits in the bending region; anda second transparent dielectric layer that covers the first transparentdielectric layer.
 16. The electronic device defined in claim 15, furthercomprising: an adhesive layer that is interposed between the firsttransparent dielectric layer and the second transparent dielectriclayer.
 17. The electronic device defined in claim 15, wherein the firsttransparent dielectric layer and the second transparent dielectric layerare attached by a plurality of welds.
 18. The electronic device definedin claim 15, further comprising: an index-matching layer that fills theplurality of slits.
 19. The electronic device defined in claim 18,wherein a first portion of the index-matching layer fills the pluralityof slits and wherein the index-matching layer has a second portion thatis interposed between the first transparent dielectric layer and thedisplay layers.
 20. The electronic device defined in claim 15, whereinthe display cover layer further comprising: a third transparentdielectric layer that has an opening that is overlapped by theplurality.